Rapid City, SD...Gillette, WY...Sheridan, WY...Dickinson, ND...Scottsbluff, NE...
MARGINAL
290,851
10,334,916
Minneapolis, MN...St. Paul, MN...Sioux Falls, SD...Green Bay, WI...Rochester, MN...
Probabilistic Graphic
Probability of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 3 Prob. Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
120,219
549,405
Rapid City, SD...Gillette, WY...Sheridan, WY...Dickinson, ND...Scottsbluff, NE...
5 %
289,782
10,308,464
Minneapolis, MN...St. Paul, MN...Sioux Falls, SD...Green Bay, WI...Rochester, MN...
SPC AC 100728
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Sat Jun 10 2017
Valid 121200Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MONDAY AFTERNOON
INTO MONDAY NIGHT NEAR THE LARAMIE AND BIG HORN MOUNTAINS INTO THE
BLACK HILLS AND SURROUNDING AREAS OF THE NORTHERN PLAINS...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
SURROUNDING AREAS OF THE ROCKIES AND PLAINS INTO PORTIONS OF THE
UPPER MIDWEST AND ADJACENT GREAT LAKES AREA...
...SUMMARY...
Severe thunderstorms are possible from the vicinity of the Laramie
and Big Horn mountains into the Black Hills, and surrounding areas
of the northern Plains, Monday afternoon into Monday night.
...Discussion...
Within the northern branch of split westerlies emanating from the
mid-latitude Pacific, ridging appears likely to continue to build
across and northeast of the Canadian Prairies. To the south, the
progressiveness of a deep closed low within the southern stream
remains in some question, but guidance does continue to indicate at
least slow movement/redevelopment northeastward across the Great
Basin toward the northern Rockies during this period. This is
forecast to support a deepening area of low pressure across parts of
eastern Montana and the Dakotas by late Monday night. An initially
stalled frontal zone across the north central Plains/Upper Midwest
likely will shift northward toward the international border through
the period, while a cold front advances east of the northern Rockies
Monday night.
Farther east, ridging within the southern stream appears likely to
remain prominent across much of the eastern U.S., while a
significant short wave continues to dig to the east of the northern
stream ridging, southeast of Hudson bay into northern Quebec. The
primary associated cold front is expected to remain well to the
north of the international border area through this period, but a
preceding influx of cooler air may advance into parts of upstate New
York and northern New England late Monday night.
...Northern Rockies/Plains...
The mid-level cold core of the closed low, and the core of the
stronger associated mid/upper jet, may remain largely displaced to
the west of the region through much of this period. However,
pronounced veering of wind fields with height, from low-level
easterlies to modest southerly mid-level flow (on the order of
30-40+ kt) is expected to contribute to sufficient shear for
organized convective development. This will occur as moistening
within the low-level easterlies, beneath steep lower/mid
tropospheric lapse rates, contributes to appreciable CAPE on the
order of 1000-2000 J/kg.
Orographic forcing near/east of the Laramie and Big Horn mountains
may support initiation of storms, before activity increases further
in the presence of increasing synoptic forcing for upward vertical
motion (associated with strengthening warm advection beneath
divergent upper flow, downstream of the closed low) by Monday
afternoon. This environment is expected to be conducive to
supercells, then perhaps considerable upscale convective growth into
one or two organizing clusters spreading across the Black Hills and
adjacent areas of the northern Plains by Monday night.
...Upper Mississippi Valley/adjacent Great Lakes...
Coverage of potential storm development remains more unclear than
across the northern high Plains region, but the environment may be
conducive to isolated/widely scattered strong to severe storm
development within a zone of warm advection along/north of the
retreating frontal zone Monday into Monday night.
..Kerr.. 06/10/2017
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